Tube drawing apparatus



Feb. 22, 19385.

IN VEN TGR.

kS. D. INSCHO TUBE DRAWING APPARATUS Filed May 9, 1934 "Patented Feb. 22, 193sv j UNITED STATES PATENT OFFICE TUBE DBIASVSPPARATUS Sidney D. Inscho, Shelby, Ohio Claims.

This invention relates to themanufacture of tubular blanks and particularly to the reduction and elongation of tubular blanks, particularly seamless tubing, by so-called cold drawing op- 5 erations.

An object of the present invention is to provide an improved method and apparatus for reducing and elongating ltubular blanksvby cold 'drawing operations and whereby the -frictional resistance yor surface drag set up as the blank is drawn through the die is materially lessened, 4 thus providing a more efcient drawing operation, improving the characteristics of the final product, and increasing the life ofthe apparatus.

A further object ofthe invention is to provide an apparatus having means adapted to grip the forward end of the blank for drawing the latter through a reducing die and also having a yieldingly mounted-resistance means adapted to grip the rear end of the blank so as to resist or oppose the forward travel of the blank, the latter means thus exerting a resistanceforce, tending to stretch the fibers of the metal at the locality of the die and to-relieve the frictional or surface drag on the blank at that point. rAs a consequence less power is required to draw the blank through the die to effect elongation thereof and reduction of the wall thickness. Moreover, by relieving or lessening the-frictional resistance to the passage of the blank through the die, im-

proved inner and outer surface characteristics of the blank are secured.

It is a well recognized fact that a cold drawing operation requires considerable power for pulling the tubular blank through the die to effect reduction vthereof to the diameter of the internal mandrel. Ordinarily, before each drawing operation, the blank is carefully annealed so that the metal will not be subjected to undue strain or be fractured during the drawing operation. The tubular blank must be well lubricated to avoid injury not only to the inner and outer surfaces of the tube but also to the die and mandrei. Even though the die and mandrel are made of high grade material, carefully prepared and accurately finished, they are subject to rapid wear and hence the maintenance thereof becomes a costly item. Even greater diiculties are encountered in the reduction of stainless steel tubes, particularly those of certain analyses, this tubing being very difficult to cold draw due to the physical characteristics thereof. In cold drawing stainless steel tubes it has been found that increased difficulties arise owing to the difficulty (o1. zus-"1) in nding a lubricant that will give its surface sufficient smoothness to offset the resistance set up by the die and mandrel during the cold drawing operation.

'Ihe present invention to a material extent overcomes the foregoing difcultiessince in ae'- cordance therewith considerable of the surface drag and resistance' set up at the locality of the die is eliminated.

Other objects of this invention will appear in the following description and appended claims, reference being had tothe accompanying drawing forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

Fig. 1 is a .plan View, partly in sectiomci an apparatus for carrying out the present invention.

Fig. 2 is a side elevation of the construction showninFig. 1. v

Fig., 3 is a fragmentary enlarged side elevation, partly in section. of the apparatus.

Fig. 4 is an enlarged sectional view illustrating the die and the manner in. which the tube is reduced.

Before explaining in detail the present invention it is to be understood that the invention is not limited in its application to the 'details of` construction and arrangement of parts illustrated in the accompanying drawing, since the invention is capable of other embodiments and of being practiced or carried out in various 'ways Also it is to be understood that the phraseology or, terminology employed lherein is for the purpose of description and not of limitation, and it is not intended to limit the invention claimed herein beyond the requirements of the prior art.

In the drawing there is illustrated, by way of example, an apparatus for carrying out the present method, this apparatus comprising a draw bench I0 upon which is mounted a gripping device or pulling head II forgripping one end of the tubular blank B. One en d of a rack I2 is suitablyconnected tothe gripping device Il and the latter is provided with suitable guide rolls I3 for guiding the same longitudinally in a predetermined path on the bench I0. The forward end of the benchfhas an' upstandlng abutment I4 forming a stop for limiting the forward travel of the pulling head1 I. The rack I2 isadapted to engagea rack"'gear I5 fixed upon a shaft I6 suitably mountedfor rotation in a machine vII of the pinch roll type. 'I'he forward end of lthe rack I2 carries a guide roll I 8 mounted to travel upon a suitable support I9. Power is suppliedvtrr` .move the rack I2 longitudinally by means Vof a" variable speed motor 20 .through a gear reduction unit 2| having a gear 22 meshing with a gear 23 fixed upon the end of the cross-shaft |6. A suitable control device 24 may be associated with the motor 2li to control the electrical energy supplied thereto.

A suitable support 3G is spaced from one end of the draw bench i0 and in alinement therewith. Movably mounted upon this support by cuide rollers, as illustrated, is a second gripping device or pulling head 3| which is adapted to grip the rear end of the tubular blank B while permitting free longitudinal movement therein of a mandrel 33 carried by the gripping device or pulling head il. The pulling head 3| is connected by pull rods 34, which straddle the mandrel 33, to a yoke 35 fixed upon one end of a piston rod 36 slidably mounted in the hydraulic cylinder 3l. A piston 38 is secured to the inner end of the piston rod 3 6 and is adapted to reciprocate within the bore of the cylinder against a body of oil or other suitable fluid medium. The hydraulic cylinder 31 is provided with a by-pass pipe 40 communicating with the interior of the cylinder at opposite ends of the piston, and in the length of this pipe there is located a suitable control valve 4| by which the flow of oil from one side of the piston to the other may be controlled so as to Vary the resistance of the piston to the longitudinal travel of pulling head 3|.

Mounted on the rear end of the draw bench l0 and fastened thereto is a die head 42 which has a control opening 43 counterbored to receive a circular die 4t centrally apertured for the passage therethrough of the tube B and mandrel 33.

The central annular opening in the die 44 is of materially less diameter than the initial diameter of the tubing B before reduction and elongation thereof, the die as shown having a constricted opening which is of flared or tapered formation as illustrated, for example, in Flg. 4.

Preparatory to the operation of the machine,

the tubuiar blank B 1s pointed at its forward end and inserted through the constricted opening in the die 44 and is clampedin the Jaws of the pulling head or gripping device II which at that time is initially positioned adjacent the die head 42. 'Ihe opposite end of the blank B is gripped by the clamping ,laws of the gripping device or pulling head 3|. It is understood that the mandrel 33 is positioned within the blank and with the latter is gripped at the same time at its forward end by the head Power is supplied to cause the pulling head and the blank B together with the mandrel 33 to move in the direction indicated by the arrows in Fig. 3. This movement is resisted but not prevented by the rear 'pulling head 3| through the action of the piston 33 in the cylinder 31. As a consequence the blank is subjected to tension or stretching action and the gripping device 3| is caused to move in the direction of the arrows in Fig. 3 but at a slower rate than the gripping device Il.

mouth of the die is materially weaker than at anyupoint rearwardly thereof, I have found that by exerting a rearward pulling or resistance force on the blank at the rear side of the die and in opposition to the forward pulling force exerted by the head Ii, the bers of the metal at the reduction point C may be placed under sunlcient ten-v sion to effect a stretching of the tubing, and this stretching force is consolidated at this weakest point in the blank. Thus, the moving resistance force due to the head 3| is consolidated at the weakest point in the blank, i. e. at the point of reduction in wall thickness at the mouth of the die, and the result of this rearwardly directed longitudinal force is to effect a definite stretching of the bers of the metal at this locality. 'I'he head 3|, of course. travels forwardly as the tube is pulled through the die, but the resistance set up by the piston 38 is adjusted so as to exert the required stretch on the blank. It will be readily seen therefore, that by virtue of the foregoing the drawing operation is materially assisted. The die isv relieved of considerable friction and willconsequently have a longer life. The frictional drag on the blanklis materially reduced thus improving its surface characteristics and reducing the power required for the cold drawing operation.

When the clamp or pulling head 3| reaches,`

during its forward travel, the die head 42, the jaws of the clamp or gripping device 3| are automatically released by suitable automatic means, not shown, thereby releasing the tubing B and permitting the rear terminal end to pass on through the die opening.

I claim:

1. In an apparatus for reducing and elongating a tubular blank, the combination of a die having a restricted opening through which the blank is drawn to reduce and elongate the same, separate devices for continuously applying opposed forces to said blank at opposite sides of said die, said devices being relatively movable whereby adjacent local portions of the blank at the locality of the die are subjected to stretching action, and a mandrel movable with the elongated portions of the blank for controlling/the inner diameter thereof and Acontrolling longitudinal strain thereon.

2. In an apparatus for reducing and elongating a tubular blank, the combination of a die having a restricted opening through which the blank is drawn to reduce and elongate the same, separate devices for continuously applying opposed forces to said blank at opposite sides vof said die, said devices being relatively movable whereby adjacent local portions of the blank at the locality of the die are subjected to stretching action, a mandrel movable with the elongated portions of the blank for controlling the inner diameter thereof, and means for varying the pposing force exerted'by one of said devices.

3. In an apparatus for reducing the wall thickness of a blank and elongating the same, the combination of a die having a restricted opening through which a tubular blank of larger diameter is drawn to reduce and elongate the same, means exerting a longitudinal force on the blank for drawing said blank through the die. means exerting an opposing force of less magnitude for stretching the blank at the point of reduction thereof in the die, and means for limiting said stretching action to the locality of saidpoint of reduction.

4. In an apparatus for reducing the wall thickness bf a blank and elongating thasame, the comthrough which a tubularblank of larg-er diameter is drawn, a mandrel located interiorly of said blank, a device adapted to be attached to said mandrel and bla'nk adjacent the forward end thereof for drawing the said mandrel and blank through the die, and a device adapted to be attached to the blank adjacent the rear end thereof 'for resisting the travelo! the blank through the tached to the blank adjacent Vthe rear end thereof and movable therewith but at. a lesser rate of speed than said first named device for resisting the travel of the blank through the die.

6. `In an apparatus for reducing the wall thickness of a. blank and elongating the same, the combination of a stationary die having an opening through which a tubular blank of larger diameter is drawn, a mandrel located interiorly of said blank, a device adapted to be attached to said mandrel and blank adjacent the forward end thereof f or drawing the said mandrel and blank through the' die, a device adapted to be attached to the blank adjacent the rear end thereof and movable'therewith but at a lesser rate of speed than said first named device for resisting the travel of the blank through the die, and means for varying the resistance. force exerted by said second named device. j

7. In an apparatus for reducing the wall thickness of a tubular blank and elongating the same, the combination of a die having an opening through which a tubular blank of larger diameter ,is drawn to reduce and elongate the same, a forwardly travelling device for pulling the blank through the die, a forwardly travelling device adapted to be secured to the blank adjacent'the rear end thereof, hydraulic means connected to said last named device for yieldingly resisting the travel thereof, and means for varying the resistanceof said hydraulic means. v

8.`In an apparatus of the class described, the combination of a die having an opening through which a tubular blank of larger diameter is drawn to reduce and elongate the same, la mandreljlocated within said blank, a forwardly .traveling pulling head adapted-to grip the forward end of the blank and mandrel for pulling the same through the die, a rear pulling head attachable at the rear end of the blank for resisting the forward travel of the blank, and an hydraulic piston operatively connected to said rear travelling head for applying a yieldable force effective to resist but not prevent movement of the blank. j A

9. In an apparatus of thel class described, the combination of a die having an opening through which a tubular blank of larger diameter is drawn to redu and elongate the same, pulling members adapted to be operatively connected to the blank vat opposite sides of said die, both of said members being mounted to travel in the same direction but at different rates of speed whereby said blank will be progressively stretched at its 'point of reduction in the die, and means for controlling the internal diameterof the reduced portionsof f the blank and for limiting longitudinal' 'strain thereon.

l0. In an apparatus for reducing and elongat- 'blank at the point of the reduction thereof, andmeansv whereby the effective stretching of the blank will be localized at said weakened point.

, SIDNEY D. INSCHO. 

